How Do Magnets Work

How Do Magnets Work

We have all played with magnets from time to time. Every time you do, you have asked yourself ‘how do magnets work?’ Many of us understand that magnets have two different charges and that like charges repel each other, but that still does not explain how a magnet works. Below is an attempt to explain the basics behind the secret inner workings of the mysterious magnet.

A magnet is any material or object that produces a magnetic field. This magnetic field is responsible for the property of a magnet: a force that pulls on other ferromagnetic materials and attracts or repels other magnets. A permanent magnet is an object made from a material that is magnetized and creates its own persistent magnetic field. Materials that can be magnetized, which are strongly attracted to a magnet, are called ferromagnetic. Although ferromagnetic materials are the only ones attracted to a magnet strongly enough to be commonly considered magnetic, all other substances respond weakly to a magnetic field.

Some facts about magnets include:

  • the north pole of the magnet points to the geomagnetic north pole (a south magnetic pole) located in Canada above the Arctic Circle.
  • north poles repel north poles
  • south poles repel south poles
  • north poles attract south poles
  • south poles attract north poles
  • the force of attraction or repulsion varies inversely with the distance squared
  • the strength of a magnet varies at different locations on the magnet
  • magnets are strongest at their poles
  • magnets strongly attract steel, iron, nickel, cobalt, gadolinium
  • magnets slightly attract liquid oxygen and other materials
  • magnets slightly repel water, carbon and boron

The mechanics of how do magnets work really breaks right down to the atomic level. When current flows in a wire a magnetic field is created around the wire. Current is simply a bunch of moving electrons, and moving electrons make a magnetic field. This is how electromagnets are made to work.

Around the nucleus of the atom there are electrons. Scientists used to think that they had circular orbits, but have discovered that things are much more complicated. Actually, the patterns of the electron within one of these orbitals takes into account Schroedinger’s wave equations. Electrons occupy certain shells that surround the nucleus of the atom. These shells have been given letter names K,L,M,N,O,P,Q. They have also been given number names, such as 1,2,3,4,5,6,7(think quantum mechanics). Within the shell, there may exist subshells or orbitals, with letter names such as s,p,d,f. Some of these orbitals look like spheres, some like an hourglass, still others like beads. The K shell contains an s orbital called a 1s orbital. The L shell contains an s and p orbital called a 2s and 2p orbital. The M shell contains an s, p and d orbital called a 3s, 3p and 3d orbital. The N, O, P and Q shells each contain an s, p, d and f orbital called a 4s, 4p, 4d, 4f, 5s, 5p, 5d, 5f, 6s, 6p, 6d, 6f, 7s, 7p, 7d and 7f orbital. These orbitals also have various sub-orbitals. Each can only contain a certain number of electrons. A maximum of 2 electrons can occupy a sub-orbital where one has a spin of up, the other has a spin of down. There can not be two electrons with spin up in the same sub-orbital(the Pauli exclusion principal). Also, when you have a pair of electrons in a sub-orbital, their combined magnetic fields will cancel each other out. If you are confuse, you are not alone. Many people get lost here and just wonder about magnets instead of researching further.

When you look at the ferromagnetic metals it is hard to see why they are so different form the elements next to them on the periodic table. It is generally accepted that ferromagnetic elements have large magnetic moments because of un-paired electrons in their outer orbitals. The spin of the electron is also thought to create a minute magnetic field. These fields have a compounding effect, so when you get a bunch of these fields together, they add up to bigger fields.

To wrap things up on ‘how do magnets work?’, the atoms of ferromagnetic materials tend to have their own magnetic field created by the electrons that orbit them. Small groups of atoms tend to orient themselves in the same direction. Each of these groups is called a magnetic domain. Each domain has its own north pole and south pole. When a piece of iron is not magnetized the domains will not be pointing in the same direction, but will be pointing in random directions canceling each other out and preventing the iron from having a north or south pole or being a magnet. If you introduce current(magnetic field), the domains will start to line up with the external magnetic field. The more current applied, the higher the number of aligned domains. As the external magnetic field becomes stronger, more and more of the domains will line up with it. There will be a point where all of the domains within the iron are aligned with the external magnetic field(saturation), no matter how much stronger the magnetic field is made. After the external magnetic field is removed, soft magnetic materials will revert to randomly oriented domains; however, hard magnetic materials will keep most of their domains aligned, creating a strong permanent magnet. So, there you have it.

We have written many articles about magnets for Universe Today. Here’s an article about bar magnets, and here’s an article about super magnets.

If you’d like more info on magnets, check out some cool experiments with magnets, and here’s a link to an article about super magnets by Wise Geek.

We’ve also recorded an entire episode of Astronomy Cast all about Magnetism. Listen here, Episode 42: Magnetism Everywhere.

Wise Geek
Wikipedia: Magnet
Wikipedia: Ferromagnetism

Why Is The Sunset Red?



Why is the sunset red? Awesome question. The most basic answer is that light is refracted by particles in the atmosphere and the red end of the spectrum is what is visible. To better understand that you have to have a basic understanding of how light behaves in the air, the atmosphere’s composition, the color of light, wavelengths, and Rayleigh scattering and here is all of the information that you need to understand those things.

The Earth’s atmosphere is one of the main factors in determining what color a sunset is. The atmosphere is made up mostly of gases with a few other molecules thrown in. Since it completely surrounds the Earth it affects what you see in every direction. The most common gasses in our atmosphere are nitrogen(78%) and oxygen(21%). The remaining single percent is made up of trace gasses, like argon, and water vapor and many small solid particles, like dust, soot and ashes, pollen, and salt from the oceans. There may be more water in the air after a rainstorm, or near the ocean. Volcanoes can put large amounts of dust particles high into the atmosphere. Pollution can add different gases or dust and soot.

Next, you have to look at light waves and the color of light. Light is an energy that travels in waves. Light is a wave of vibrating electric and magnetic fields and is a part of the electromagnetic spectrum. Electromagnetic waves travel through space at the speed of light(299,792 km/sec). The energy of the radiation depends on its wavelength and frequency. A wavelength is the distance between the tops of the waves. The frequency is the number of waves that pass by each second. The longer the wavelength of the light, the lower the frequency, and the less energy it contains. Visible light is the part of the electromagnetic spectrum that our eyes can see. Light from a light bulb or the Sun may look white, but it is actually a combination of many colors. Light can be split into its different colors with a prism. A rainbow is a natural prism effect. The colors of the spectrum blend into one another. The colors have different wavelengths, frequencies, and energies. Violet has the shortest wavelength meaning that it has the highest frequency and energy. Red has the longest wavelength and lowest frequency and energy.

In order to put it all together, we have to look at the action of light in the air of our planet. Light moves in a straight line until it is interfered with(gas molecule, dust, or anything else). What happens to that light depends on the wavelength of the light and size of the particle. Dust particles and water droplets are much larger than the wavelength of visible light, so it bounces off in different directions. The reflected light appears white because it still contains all of the same colors, but gas molecules are smaller than the wavelength of visible light. When light bumps into them it acts differently. After light hits a gas molecule some of it may get absorbed. Later, the molecule radiates the light in a different direction. The color that is radiated is the same color that was absorbed. The different colors of light are affected differently. All of the colors can be absorbed, but the higher frequencies (blues) are absorbed more often than the lower frequencies (reds). This process is called Rayleigh scattering.

Long story short,, the answer to ‘why is the sunset red?’ is: At sunset, light must travel farther through the atmosphere before it gets to you, so more of it is reflected and scattered and the sun appears dimmer. The color of the sun itself appears to change, first to orange and then to red because even more of the short wavelength blues and greens are now scattered and only the longer wavelengths(reds, oranges) are left to be seen.

We have written many articles about the sunset for Universe Today. Here’s an article about sunrise and sunset, and here are some sunset pictures.

If you’d like more info on the Sun, check out NASA’s Solar System Exploration Guide on the Sun, and here’s a link to the SOHO mission homepage, which has the latest images from the Sun.

We’ve also recorded an episode of Astronomy Cast all about the Sun. Listen here, Episode 30: The Sun, Spots and All.

NASA Space Place

Where do Hurricanes Occur?

View of Hurricane Ike From Space Station

What is a hurricane? Well, a hurricane is a tropical cyclone that occurs in the North Atlantic Ocean or the Northeast Pacific Ocean and remains east of the International Dateline. Tropical cyclones are characterized by a large low pressure center and numerous thunderstorms. These produce strong winds and heavy rain. These cyclones feed on heat released when moist air rises causing condensation of the water vapor that is contained in the moist air. These storms are fueled by a different heat mechanism than other cyclonic windstorms(nor’easters, polar lows, and European windstorms). They are classified as a warm core storm system.

All tropical cyclones are areas of low atmospheric pressure. As a matter of fact, the pressures recorded at the center of tropical cyclones are among the lowest that occur at sea level. A hurricane is characterized and driven by the release of large amounts of latent heat of condensation(water vapor condenses as it moves upward). This heat is distributed vertically around the center of the storm, so, except at the surface of water, it is warmer inside the cyclone than it is outside. At the center of the hurricane is an area of sinking air. If this area is strong enough, it can develop into a large eye. Weather in the eye is normally calm and free of clouds, but the surface of the sea may be tossing violently. The eye is normally circular in shape, and may range in size from 3 km to 370 km in diameter.

While a tropical cyclone’s primary energy source is the release of the heat of condensation, solar heating is the initial source of that evaporation. An initial warm core system(an organized thunderstorm complex) is necessary for the formation of a tropical cyclone, but a large flux of energy is needed to lower atmospheric pressure. The influx of warmth and moisture from the underlying ocean surface is critical for tropical cyclone strengthening and most of it comes from the lower 1 km of the atmosphere. Condensation leads to higher wind speeds. These faster winds and the lower pressure associated with them cause an increase in surface evaporation and more condensation. This positive feedback system continues and feeds the hurricane until the conditions for hurricane formation are gone. The rotation of Earth causes the system to spin,(the Coriolis effect) which gives it a cyclonic appearance and affects its trajectory.
Tropical cyclones are distinguished by the deep convection that fuels them. Since convection is strongest in the tropics it defines the initial domain of the tropical cyclone. To continue to feed itself a tropical cyclone must remain over warm water. When a tropical cyclone passes over land, it is cut off from its heat source and its strength diminishes rapidly. The passage of a tropical cyclone over the ocean can cause the upper layers of the ocean to cool substantially, which can influence subsequent cyclone development. Scientists at the National Center for Atmospheric Research in the US estimate that a tropical cyclone releases heat energy equal to 70 times the world energy consumption, 200 times the worldwide electrical generating capacity, or the same as exploding a 10 megaton nuclear bomb every 20 minutes.
Well, there you have the answer to what is a hurricane. It is a tropical nightmare, but if humans could somehow harness that energy we would never need fossil fuels again.

We have written many articles about hurricanes for Universe Today. Here’s an article about human influences generating more hurricanes, and here’s a NASA video of Hurricane Bill.

If you’d like more info on hurricanes, check out Visible Earth Homepage. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

How Do Tornadoes Form?

Tornado in Kansas

How do tornadoes form? That is pretty easy to answer since there has been a large amount of study into the subject. They are usually the extreme result of a supercell thunderstorm. During the storm cold air and warm air combine in a set pattern: the cold air drops as the warm air rises. The warm air eventually twists into a spiral and forms the funnel cloud that we all associate with a tornado.

The formation of a tornado follows a clear set of steps. First there a change in wind direction and an increase in wind speed. This change occurs at an increasing altitude and creates an invisible horizontal spinning effect in the lower atmosphere. Next, rising air within the thunderstorm’s updraft tilts the rotating air from horizontal to vertical. Third, an area of rotation, 3-10 km wide is contained within a vast majority of the storm. This is where the strongest tornadoes form. Then a lower cloud base in the center of the storm becomes a rotating wall cloud. This area can be nearly rain-free. Lastly, a tornado develops and starts to wreak its destruction.

Once a tornado has formed, it follows a predictable life cycle. First, the mesocyclone(rotating air), along with the rear flank downdraft( RFD), starts moving towards the ground. A small funnel appears to build up at the bottom of a wall cloud. As the RFD reaches the ground, the surrounding dirt rises up, causing damage even to heavy objects. The funnel touches the ground immediately after the RFD, forming a tornado.

During the next stage the tornado’s main source of energy, the RFD, begins to cool. The distance the tornado covers, depends on the rate at which the RFD cools. If the RFD cannot further provide any more warm air to the tornado, it begins to die.

Lastly, with the tornado’s warm air supply cut, the vortex begins to weaken and shrivel away. As the tornado weakens, the mesocyclone also starts to dissipate, but a new mesocyclone can start very close to the dying one. Those are the basics of tornado formation and life.

We have written many articles about tornado for Universe Today. Here’s an article about the biggest tornado, and here’s an article about the Tornado Alley.

If you’d like more info on tornado, check out the National Oceanic and Atmospheric Administration Homepage. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

How Big Is Neptune

Are There Oceans on Neptune


There are many ways to determine ‘how big is Neptune’. It has an equatorial radius 24,764 km, a polar radius of 24,341 km, and a surface area of 7.6408×10,sup>9km2. It has a volume of 6.254×1013km3, a mass of 1.0243×1026kg, and a mean density of 1.638 g/cm3. Now that you know most of the planet’s critical digits, here is a little information about its make up.

Neptune is the eighth and farthest planet from the Sun. It is the fourth-largest planet by diameter and the third-largest by mass. Neptune’s mass is 17 times that of the Earth. On average, Neptune orbits the Sun at a distance of 30.1 astronomical units. It was discovered on September 23, 1846. Neptune was the first planet found by mathematical prediction rather than direct observation. Alexis Bouvard deduced its existence from gravitational perturbations in the orbit of Uranus. The planet was later observed by Johann Galle. Its largest moon, Triton, was observed a short time later.

Neptune’s atmosphere is composed primarily of hydrogen and helium along with traces of hydrocarbons and nitrogen. It also contains a high proportion of ices like: water, ammonia, and methane. Astronomers occasionally categorize Neptune as an ice giant. The interior of Neptune, like that of Uranus, is primarily composed of ices and rock. Traces of methane in the outermost regions in part account for the planet’s blue appearance. Neptune’s atmosphere is notable for its active and visible weather patterns. When Voyager 2 flew by the planet’s southern hemisphere possessed a Great Dark Spot. These weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 km/h.Because of its great distance from the Sun, Neptune’s outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching ?218°C. Temperatures at the planet’s center are approximately 5,000°C.

Neptune has a planetary ring system. The rings may consist of ice particles coated with silicates or carbon-based material, which gives them a reddish hue. The three main rings are the narrow Adams Ring, 63,000 km from the center of Neptune, the Le Verrier Ring, at 53,000 km, and the broader, fainter Galle Ring, at 42,000 km. A faint outward extension to the Le Verrier Ring has been named Lassell; it is bounded at its outer edge by the Arago Ring at 57,000 km. Not only is the planet large, but it has many interesting features as well.

We have written many articles about Neptune for Universe Today. Here’s an article about the color of Neptune, and here are some pictures of Neptune.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We’ve also recorded an entire episode of Astronomy Cast all about Neptune. Listen here, Episode 63: Neptune.

Source: NASA

What is Gravitational Force?

Why Do Planets Orbit the Sun

Newton’s Law of Universal Gravitation is used to explain gravitational force. This law states that every massive particle in the universe attracts every other massive particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. This general, physical law was derived from observations made by induction. Another way, more modern, way to state the law is: ‘every point mass attracts every single other point mass by a force pointing along the line intersecting both points. The force is proportional to the product of the two masses and inversely proportional to the square of the distance between the point masses’.

Gravitational force surrounds us. It is what decides how much we weigh and how far a basketball will travel when thrown before it returns to the surface. The gravitational force on Earth is equal to the force the Earth exerts on you. At rest, on or near the surface of the Earth, the gravitational force equals your weight. On a different astronomical body like Venus or the Moon, the acceleration of gravity is different than on Earth, so if you were to stand on a scale, it would show you that you weigh a different amount than on Earth.

When two objects are gravitational locked, their gravitational force is centered in an area that is not at the center of either object, but at the barycenter of the system. The principle is similar to that of a see-saw. If two people of very different weights sit on opposite sides of the balance point, the heavier one must sit closer to the balance point so that they can equalize each others mass. For instance, if the heavier person weighs twice as much as the lighter one, they must sit at only half the distance from the fulcrum. The balance point is the center of mass of the see-saw, just as the barycenter is the balance point of the Earth-Moon system. This point that actually moves around the Sun in the orbit of the Earth, while the Earth and Moon each move around the barycenter, in their orbits.

Each system in the galaxy, and presumably, the universe, has a barycenter. The push and pull of the gravitational force of the objects is what keeps everything in space from crashing into one another.

We have written many articles about gravitational force for Universe Today. Here’s an article about gravity in space, and here’s an article about the discovery of gravity.

If you’d like more info on Gravity, check out The Constant Pull of Gravity: How Does It Work?, and here’s a link to Gravity on Earth Versus Gravity in Space: What’s the Difference?.

We’ve also recorded an entire episode of Astronomy Cast all about Gravity. Listen here, Episode 102: Gravity.

What Is Water Made Of



The answer to ‘what is water made of’ is as easy as you want it to be. Do you want to just do some superficial research or do you want to look a little deeper? Superficially, pure, distilled water is composed of 2 hydrogen atoms and 1 oxygen atom. If the sample of water is not ‘pure’, the composition of the sample can be different.

Salt water obviously contains salt, but it can contain many other trace elements. Fresh water from different sources will contain different elements and minerals. These come from the rocks the water washes over and the pollutants from farms and industry. The water that you drink will contain several additives used for purification plus the fluoride that is added for our health. Rain water will have any number of pollutants that have accumulated in the atmosphere.

At high temperatures and pressures, like those in the interior of giant planets, scientists think that water exists as ionic water in which the molecules break down into a soup of hydrogen and oxygen ions, and at even higher pressures as superionic water in which the oxygen crystallizes but the hydrogen ions float around freely within the oxygen lattice.

There are many interesting facts about water. Water is a tasteless, odorless liquid. The natural color of water and ice is slightly blue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas. Since the water molecule is not linear and the oxygen atom has a higher electronegativity than hydrogen atoms, water carries a slight negative charge. As a result, water has a electrical dipole moment. Water can form a large number of intermolecular hydrogen bonds(four). These factors lead to to water’s high surface tension and capillary forces. Water is often referred to as the universal solvent. All major cellular components are dissolved in water. Water is at its maximum density at 3.98°C. Oddly, it becomes less dense when it is cooled down to its solid form, ice. It expands to occupy 9% greater volume in this solid state, which accounts for the fact of ice floating on liquid water.

Water covers the majority of our planet and can be found in one form or another throughout the known universe. No matter where you are on Earth, water affects you in some way each day.

We have written many articles about water for Universe Today. Here’s an article about the density of water, and here’s an article about the water on Earth.

If you’d like more info on Water, check out NASA’s Water, Water, Everywhere!. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Source: Wikipedia

What Is The Largest Island In The World

Greenland. Image credit: NASA


If you were asked what is the largest island in the world, what would you say? Australia maybe? Greenland is the worlds largest island. While Australia is an island, it is considered a continent. Greenland has an area of 2,166,086 square km, but a meager population of 56,452. The populations is over 85% Inuit. The remaining inhabitants are mainly Danish. The average annual temperature of Greenland varies between -9 to 7 °C.

Greenland is an autonomous country within the Kingdom of Denmark. Greenland is a group of islands and Greenland is the name of the largest, most populated one. Greenland has been inhabited on and off since 2500 BC. Denmark established rule in the 18th century. In 1979 Denmark granted home rule, in a relationship known as the Commonwealth of the Realm and in 2008 Greenland voted to transfer more powers to the local government. The Danish royal government is only in charge of foreign affairs, security, financial policy, and providing a subsidy to each citizen.

Greenland is bordered by the Atlantic Ocean to the southeast, the Greenland Sea to the east, the Artic Ocean to the north, and Baffin Bay to the west. The nearest countries to Greenland are Iceland to the east and Canada to the west. The country also contains the world’s largest national park. Scientists have thought for decades that the ice sheet covering the country may actually conceal three separate island land masses that have been bridged by glaciers over the last geologic cooling period.

The Greenland ice sheet covers 1,755,637 square km. It has a volume of 2,850,000 cubic km. Gunnbjorn Fjeld is the highest point on Greenland at 3,700 m. The majority of Greenland is less than 1,500 m in elevation. The weight of the ice sheet has formed a basin that is more than 300 m below sea level.

Between 1989 and 1993, climate researchers drilled into the summit of Greenland’s ice sheet, obtaining a pair of 3 km ice cores. Analysis of the layering and chemical composition of the cores has provided a revolutionary new record of climate change going back about 100,000 years. It illustrated that the world’s weather and temperature have often shifted rapidly from one stable state to another. The glaciers of Greenland are also contributing to a rise in the global sea level at a faster rate than was previously believed.

Greenland is fascinating and intimidating at the same time. To live there is a daily struggle against the elements that has forged a tough people.

We have written many articles about Greenland for Universe Today. Here’s an article about the growing ice sheets in Greenland, and here are some images of Greenland from space.

If you’d like more info on Earth’s islands, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

World Atlas

What Is The Largest Continent

Asia Image Credit: NASA's Blue Marble project


There are a few different ways to answer ‘what is the largest continent’. The first is by area and another is by population. By area, Asia is the largest continent at 44,391,162 square km. It is also the largest by population with more than 4 billion people.

There is quite a bit of debate as to how many continents there are. Some areas of the world combine Asia and Europe into one continent called Eurasia. In that case, the continent of Eurasia would be the biggest continent in both area and population.

The debate as to how many continents there are is based in the basic, yet confusing definition of what a continent is. A continent is understood to be large, continuous, discrete mass of land, ideally separated by an expanse of water. Many of the seven most commonly recognized continents identified by convention are not discrete landmasses separated by water. The criteria of being large is used arbitrarily. Greenland has an area of 2,166,086 square km and is considered an island. Australia has an area of 7,617,930 square km, but it is called a continent. The distinct landmass separated by water criteria is sometimes ignored in the case of Europe and Asia. All of the criteria are a consensus, not a rule, so some countries teach a different number of continents.

Whether you have been taught that there are 6 or 7 continents, you need to know that here have been changing numbers of continents since the formation of the Earth. There have been anywhere from 1 to 7 continents. As the tectonic plates have shifted, the continents have broken apart and collided together again. The Earth’s tectonic plates are still moving, so it is hard to predict how many continents there will be in 500,000 years, 1 million years, and so forth.

The answer to ‘what is the largest continent’ is pretty cut and dry. If you consider that there are seven continents, then Asia is the largest in area and population. If you combine Europe and Asia into the continent of Eurasia, it is still the largest by area and population.

We have written many articles about Continent for Universe Today. Here’s an article about the number of continents in the Earth, and here’s an article about the Continental Drift Theory.

If you’d like more info on continents, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.


What Is the Coriolis Effect

Coriolis Effect


The Coriolis effect is one of those terms that you hear used from time to time, but it never seems to get fully explained, so you are left wondering ‘what is the Coriolis effect?’ The Coriolis effect is the apparent curvature of global winds, ocean currents, and everything else that moves freely across the Earth’s surface. The curvature is due to the rotation of the Earth on its axis. The effect was discovered by the nineteenth century French engineer Gaspard C. Coriolis. He used mathematical formulas to explain that the path of any object set in motion above a rotating surface will curve in relation to objects on that surface.

If not for the Earth’s rotation, global winds would blow in straight north-south lines. What actually happens is that global winds blow diagonally. The Coriolis effect influences wind direction around the world in this way: in the Northern Hemisphere it curves winds to the right; in the Southern Hemisphere it curves them left. The exception is with low pressure systems. In these systems there is a balance between the Coriolis effect and the pressure gradient force and the winds flow in reverse.

Satellites appear to follow curved paths when plotted on world maps because the Earth is a sphere and the shortest distance between two points on a sphere is not a straight line. Two-dimensional maps distort a three-dimensional surface in some way. The distortion increases with closer to the poles. In the northern hemisphere a satellite’s orbit using the shortest possible route will appear to follow a path north of the straight line from beginning to end, and then curve back toward the equator. This occurs because the latitudes, which are projected as straight horizontal lines on most world maps, are in fact circles on the surface of a sphere, which get smaller as they get closer to the pole. This happens simply because the Earth is a sphere and would be true if the Earth didn’t rotate. The Coriolis effect is of course also present, but its effect on the plotted path is much smaller, but increases in importance when calculating a trajectory or end destination. The effect becomes very important when you need to plot trajectories for missiles or artillery fire.

To sum up ‘what is the Coriolis effect’, it is an important meteorological force that is used to predict the path of storms and explains why a projectile will not hit a target at a great distance if the Earth’s rotation is not accounted for.

We have written many articles about Coriolis Effect for Universe Today. Here’s an article about the hurricane, and here’s an article about the Earth’s rotation.

If you’d like more info on Coriolis Effect, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

University of Oregon